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A layout template describes an arrangement of devices which have a set of components in common. Typically these common components are the backside layers of the devices. For example, in the Generic FET Template the Backside Adhesive, Metal Shim, Solder, and Substrate components are identified in the template as potentially being common. When one or more generic FETs is incorporated in a layout, these common components are extended between the devices and to the boundaries of the layout, as shown.
A layout template file contains parameters for the overall dimensions of the layout area, as well as the locations and orientations of the individual devices. The layout template contains links to separate device template files that describe the devices themselves. When a layout template is opened, the individual device templates are loaded and the layout model is constructed and displayed in the main window, as shown above.
To form a consistent layout, all the devices in the layout must have a consistent set of common components, materials, and boundary conditions. Devices in a valid layout will only interconnect via the common components. The parameters that specify common dimensions, such as the thicknesses of the common layers, must also be consistent. Usually, these parameters will be configured to equalize their values between devices to ensure consistency. Devices configured from a single original device template will have matching common layers with equalized parameters, and a layout of these devices will generally be consistent.
The Select submenu of the Device menu provides access to the list of devices in the layout. Each device entry consists of a device number and the title of the device, followed by the filename that device originated from, as shown in the following figure. When a device is selected in the list, the parameter lists for that device are displayed in the Device menu. If a component, history, or parameter list is open when a new device is selected, the list will switch to the corresponding list for the selected device.
Device menu and the list of devices for a MMIC power amplifier
Keyboard control of device selection is possible by using the up/down arrow keys or spacebar, or by typing a number on the list of devices. Pressing the spacebar advances to the next device in the list. Pressing the spacebar while holding down the Shift key retreats to the previous device in the list. The spacebar may also be used on the parameter lists or the main window to advance/retreat device selection. To return focus to the main window from any of the parameter lists or the list of devices, use the Esc key.
Device selection can also be performed with the mouse, by clicking on the list of devices or by clicking on the 3D model of the layout. To activate the latter approach, select the By cursor menu item from the Select submenu or use the Ctrl+D accelerator on the main window. The cursor will change to an arrow with crosshairs and the left mouse button will select the device under the cursor. The following figure shows the device selection cursor being used on the power amplifier MMIC.
The Materials list defines a common set of materials over all devices, whereas the other lists pertain to the selected device. If devices initially do not have a consistent set of materials, a set will be constructed by the union of the material lists of the individual devices. If the device templates are subsequently saved, they will each be given this unified list of materials. The Configure Run parameters (Solve menu) are also made the same for all devices. These parameters are taken from the first device, and copied into the other devices. If the devices are saved, the Configure Run parameters for each device will be these copied values.
Note: Saving devices while in a layout makes the files have the same materials and run settings.
Device selection with the cursor on a MMIC power amplifier layout
When displaying a layout template or solution, device numbers can be shown over the devices by selecting Show device numbers from the Settings menu. These device numbers are the same as those used to designate the devices in the list of devices and in the Device Layout Table. Device numbers are assigned based on the order listed in the layout template, so deleting a device results in renumbering of all devices.
Device numbers are drawn in the same color as the template wireframe. Change this color through the Template wireframe... dialog in the Settings menu.
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